Stacked color imaging devices are known which have a layer of an organic photoelectric conversion material or an inorganic photoelectric conversion material such as amorphous silicon or a compound semiconductor and mosaic color filters disposed over the photoelectric conversion layer (refer to JP-A-2005-347475 and Hitachi, Ltd., “Single-plate Color Solid-state Imaging Device Using Amorphous Si,” ITEJ Technical Report TEBS76-1-1). The photoelectric conversion layer absorbs visible light and generates signal charges.
In such stacked color imaging devices, what is called a panchromatic photoelectric conversion layer which is sensitive in the entire visible range is sandwiched between pixel electrodes and a transparent counter electrode and mosaic color filters are laid on the transparent counter electrode with a protective layer interposed in between. The mosaic filters are an arrangement of color filters that correspond to the respective pixel portions and each of which transmits R, G, or B light or Cy, Mg, or Ye light. Light shining on the imaging device is separated by the mosaic filters on a pixel-by-pixel basis into R, G, and B light beams or Cy, Mg, and Ye light beams, which are converted into signal charges by the photoelectric conversion layer. The signal charges generated by the photoelectric conversion layer are collected by the pixel electrodes, stored in charge storage diodes formed in a silicon substrate for a prescribed time via plugs that are connected to the pixel electrodes, and read out by readout circuits such as CMOS circuits or a CCD.
In such stacked color imaging devices, potential gradients are formed by applying a bias voltage between the pixel electrodes and the transparent counter electrode and almost all of signal charges generated in the photoelectric conversion layer are read out to the pixel electrode side. Therefore, a high-sensitivity imaging device having high efficiency of light utilization (the aperture ratio is close to 1) by setting the gaps between the pixel electrodes small. However, if there exists a certain distance between the photoelectric conversion layer and the mosaic color filters, light that is incident on each pixel portion obliquely may leak into adjacent pixel portions to cause color contamination.
Conventional stacked color imaging devices in which each pixel portion measures 3 to 10 μm for the mosaic color filters, the protective layer, and the panchromatic photoelectric conversion layer being 0.6 to 1.2 μm, 0.2 to 0.5 μm, and 0.3 to 1.0 μm in thickness, respectively, rarely suffer color contamination because of a small ratio of leakage of oblique incident light into adjacent pixel portions. However, the problem of color contamination will not be negligible when the degree of miniaturization of the pixel portions is increased and each pixel portion comes to measure less than 2 μm, in particular, around 1 μm, in the future.